#include <iostream>
using namespace std;
int main()
{
int i,sum,n;
sum=2020;
cout <<"n=";
cin>>n;
i=1;
while(i<=n)
{
if(i%2==1)
sum-=i;
else
sum+=i;
i++;	
}
cout <<sum<<endl;
return 0;	
}
